1. Field of the Invention
The present invention relates to a coder/decoder (“codec”), and, more particularly, to providing and operating a codes with a clock signal at a desired operational rate. More specifically, the present invention relates to generating a desired clock signal at the desired operational rate from an available external clock signal at another clock rate.
2. Description of Related Art
A (coder/decoder) (“codec”) is considered to be any technology that encodes and decodes data. The encoding and decoding of data is useful and important to the processing of data in analog, digital, and mixed signal systems. Codecs may be implemented in software, hardware, or a combination of both software and hardware. Also, an exemplary type of audio codec is the audio codec (“AC”) '97, which Intel Corporation has published in various revisions of the specification entitled Audio Codec '97 (“AC '97) (e.g., revision 2.2 in September 2000; revision 2.1 in May 22, 1998; revision 2.0 in Sep. 29, 1997; revision 1.03 in Sep. 15, 1996). The AC '97 specification and its various revisions are hereby incorporated by reference.
The AC '97 specification, revision 1.03 comprehensively defines a serial codec device that is designed to be used in systems in which audio signal processing and audio analog-to-digital (A/D) and digital-to-analog (D/A) conversions are performed in separate devices. The AC '97 specification, revision 2.0 is a follow-up revision to revision 1.03 and further defines the interface for a combined audio/telephony codec. Revision 2.0 also includes definitions for modem sample rate control, tagged data exchange using different sampling rates, general purpose input/output definitions, and extended AC-link definitions for multiple devices and power management event handling. Revision 2.1 updates revisions 1.03 and 2.0 by including some electrical and power management updates. Revision 2.2 provides further updates to revision 2.1 by adding optional S/PDIF support, standardized slot re-mapping, and updated electrical specification for better riser support.
Codecs require the use of a clock signal at an operational codec clock rate. A separate clock generating oscillator or crystal is typically utilized to provide the clock signal at the operational codec clock rate. However, the use of a separate clock generating oscillator or crystal requires an additional component to the overall codec system or chip. A separate clock generating oscillator or crystal adds to the cost of the codec (e.g., a crystal is a relatively expensive component). Furthermore, the use of an additional component, such as the separate clock, adds to the space requirement of the codec hardware. Although the desire and need is to eliminate the use of a separate clock for a codec, the use of any extra pins or additional memory requirements to implement other clocking schemes for the codec chip also needs to be minimized or eliminated.
The present invention recognizes the desire and need for eliminating the use of a separate clock, such as a clock generating oscillator or a crystal, for a codec, which would reduce the overall size and cost for the codec. In implementing a different clocking scheme, the present invention further recognizes the desire and need to minimize or reduce having to add any extra pins or additional memory to the codec chip. The present invention overcomes the problems and disadvantages that have been encountered with the prior art.